地震活动性的统计分析:由过去推测将来的可能性研究

STATISTICAL ANALYSIS OF SEISMICITY: STUDY ON THE POSSIBILITY OF EXTRAPOLATING THE FUTURE FROM THE PAST

为了由过去的地震活动性推测将来的地震活动性，引入了地震（震级≥m）的期望年发生率v（≥m）来描述一个地区的地震活动性．根据全球地震目录（1964—1994年）以及南加州（1932—1995年）和华北（1970—1994年）两个区域地震目录资料，以统计样本量作为目录记录时间长短的相对量度，对由不同的统计样本量计算得出的地震实际年发生率v（≥m，T，t）进行了统计分析，得到三点结沦：①在统计样本量n足够大的情况下，地震实际年发生率表现出准平稳时间过程的特征，可近似地看作地震期望年发生率，本文给出了这种近似的误差（离差系数）与统计样本量之间的定量关系；②离差系数与统计样本量之间的关系与震级无关，表现出不同震级层次的相似性；③统计样本量相同时，不同震级的地震期望年发生率之间满足logv（≥）=a－bm的关系，形式上与G－R关系相似，但它给出了由小地震的统计特征估计大地震的期望年发生率及其统计误差的方法．基于上述结论，进一步讨论了地震活动性的统计特征在地震危险性分析中的潜在应用。

For the purpose of extrapolating the future seismicity from the past using available earthquake catalogs, the expected annual earthquake occurrence rate (magnitude ≥m), v (≥m), is introduced to describe the seismicity of an area. Based on the 1964-1994 global earthquake catalog and two regional catalogs, i. e. the 1932-1995 South California catalog and the 1970-1994 North China catalog and taking sampling size n to represent relatively the finite record length of time of the catalog used, statistical analyses on the practical annual earthquake occurrence rate v (≥ m, T, t) have been Performed. Three results are obtained : 1. the practical annual earthquake occurrence rate can be considered as the expected annual earthquake occurrence rate for the first approximation when the sampling size is large enough.The quantitative relation between the error of this approximation (deviation coefficient)and the sampling size is obtained. 2. the relation between deviation coefficient and sampling size is independent of magnitude, exhibiting a self-similar error- relation in magnitude hierarchy. 3. a formula of log v(≥m) =a-bm, similar with G-R relation,has been established for expected annual earthquake occurrence rate and magnitude under the condition of equal sampling size, which provide the method of estimating the expected annual earthquake occurrence rate and its statistical error of large earthquakes from those of small ones. Furthermore, the potential applications of the statistical characteristics of seismicity on seismic hazard assessment are discussed.